The disclosure relates to switch mode power supplies including binary pulse skipping.
Unless otherwise indicated herein, the approaches described in this section are not admitted to be prior art by inclusion in this section.
Switching regulators are noisy. The effect can be minimized provided the switching frequency harmonics do not fall into pass bands of radio frequency (RF) receiver. A switching regulator operates by storing energy in an inductor during a power on (Pon) time, then transferring that energy to a load during an off time. There is a minimum requirement for the Pon time, in order to avoid incorrect triggering of internal comparators of the switching regulator.
Because the Pon(min) is fixed, there is a minimum amount of energy stored for each Pon pulse. For regulation, the energy must be dissipated in the load. With light loading on the switching regulator, the energy dissipation may not happen.
There are two existing approaches for handling this potential loss of regulation, namely, pulse frequency modulation (PFM), and pulse skipping in pulse width modulation (PWM) mode. PFM is asynchronous and therefore has an unknown and uncontrolled harmonic spectrum.
Pulse skipping removes pulses from the switching waveform. However, the number of pulses skipped is load dependent and effectively random. Even if predictable, e.g., the removal of two pulses in every three, the effect is that the harmonic spectrum has changed, as the fundamental is now one third of the original, and has harmonics in new positions.